The present invention relates to improvements in the electro-acoustic signalling horns employed in the automobile industry as sound warning devices.
These horns are constituted by a case containing an electromagnetic system which imparts a vibratory oscillation to a diaphragm, and a sound box having a labyrinth chamber facing the diaphragm. The diaphragm is clamped between the case and the box, the latter part usually being made from a plastics material.
It has been proposed to construct the box in two parts and to assemble one of these parts with the diaphragm and the case through the agency of a clipping band and then to weld or adhere the second part to the first part. The clipping thus obtained is not very precise and very sensitive to conditions of temperature, hygrometry, etc., since the clipping band bears against a part of plastics material which is itself very sensitive to these conditions. Moreover, there are a large number of parts to assemble and a large number of operations and this increases the price and decreases the output.
It has also been proposed to add to the diaphragm a metal plate which is itself secured to the case so as to obtain a metallic assembly which is of high precision but little sensitive to variations in temperature. The plate may be fixed to the sound box by moulding it on the latter, the diaphragm and the case being screwed or riveted to the plate. The box must also be constructed in two parts, which are thereafter welded or adhered together, so that the manufacture of the horn still requires a large number of operations. An object of the present invention is to avoid these drawbacks of known horns by means of a new cheaper horn which is constituted by a small number of component parts and is more easily and more rapidly assembled than the known horns.